In November 2015, the LHC delivered pp collisions at \(\sqrt{s} = 5.02\) .
The fraction of events initiated by gluon-gluon collisions grows monotonically with \(\sqrt{s}\) . It is around 73% at 5.02,
as calculated with  (v2) [1]}, [2]}, [3]} at next-to-leading order (NLO) using the NNPDF3.0 NLO [4]} parton distribution functions (PDFs),
and increases to around 86% at 13, making this new data set partially complementary to the higher-energy samples.
Measurements of production at various \(\sqrt{s}\)  probe different values of \(x\)  and thus can provide complementary information on the gluon distribution.
In addition, future measurements of \(\sigma _{}\)  in nuclear collisions at the same nucleon-nucleon center-of-mass energy [5]}, [6]}
would profit from the availability of a reference measurement in pp collisions at \(\sqrt{s} = 5.02\) , without the need to extrapolate from measurements at different \(\sqrt{s}\) .
This has already been demonstrated with the first observation of the process using proton-nucleus collisions at a higher nucleon-nucleon center-of-mass energy [7]}.
